Light emitting diode replacement lamp

ABSTRACT

In various embodiments, an illumination device includes a housing, a power connector for connecting the illumination device to a power socket and receiving input power, a light emitter for direct illumination disposed within the housing, a circuit for regulating the input power and providing the regulated power to the light emitter, and a decorative illumination element for providing decorative illumination.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/093,197, filed on Apr. 25, 2011, which is a continuation-in-part ofU.S. patent application Ser. No. 12/546,377, filed on Aug. 24, 2009, nowU.S. Pat. No. 7,946,730, which is a continuation of U.S. patentapplication Ser. No. 11/868,406, filed on Oct. 5, 2007, now U.S. Pat.No. 7,597,456, which is a division of U.S. patent application Ser. No.10/893,727, filed on Jul. 16, 2004, now U.S. Pat. No. 7,296,913, whichclaims priority to and the benefit of U.S. Provisional PatentApplication No. 60/517,130, filed on Nov. 4, 2003. The entire disclosureof each of these applications is hereby incorporated herein byreference.

TECHNICAL FIELD

In various embodiments, the present invention relates generally toillumination systems and methods incorporating light emitting diodes(LEDs), and more specifically to such systems and methods that provideboth direct illumination and decorative illumination.

BACKGROUND

Currently lighting applications are dominated by incandescent lightingproducts. Because they use hot filaments, these products produceconsiderable heat, which is wasted, in addition to visible light that isdesired. Halogen-based lighting enables filaments to operate at a highertemperature without premature failure, but again considerablenon-visible infrared light is emitted, and this heat is directed awayfrom the lamp to the extent feasible. This is conventionally done byusing a dichroic reflector shade that preferentially passes the infraredas well as a portion of the visible light. The nature of this dichroicreflector is such that it passes several different visible colors aswell as the infrared radiation, giving a somewhat pleasing appearance.This has led to numerous decorative applications for such halogenlights. These lights consume substantial current and dissipateconsiderable unwanted heat. Halogen bulbs are designed to operate at avariety of voltages between 12 volts (V) to as high 15 V or greater.

Light emitting diodes have operating advantages compared to ordinaryincandescent and halogen lights. LEDs typically emit a narrow range ofwavelengths, thereby eliminating, to a large degree, wasted non-visibleenergy. White light can be created by combining light colors. LEDs canalso emit in the ultraviolet wavelength range, in which case white light(as well as certain colors) can be created by excitation of a phosphor.

LEDs have an extremely long life compared to incandescent and halogenbulbs. Whereas incandescent and halogen bulbs may have a life expectancyof 2000 hours before the filament fails, LEDs may last as long as100,000 hours, and 5,000 hours is fairly typical. Moreover, unlikeincandescent and halogen bulbs, LEDs are not shock-sensitive and canwithstand large forces without failure, while the hot filament of anincandescent or halogen bulb is prone to rupture.

Halogen bulbs, incandescent bulbs, and LEDs all typically require afixed operating voltage and current for optimal performance. Too high anoperating voltage causes premature failure, while too low an operatingvoltage or current reduces light output. Also, the color of incandescentand halogen lights shifts toward the red end of the visible spectrum ascurrent and voltage are reduced. This is in contrast to LEDs, in whichonly the intensity of the light is reduced. Furthermore, as the voltageto an incandescent or halogen light is reduced, its temperature drops;as a result, its internal resistance decreases, leading to highercurrent consumption but without commensurate light output. In caseswhere batteries are used as the source of energy, they can be drainedwithout producing visible light.

Incandescent and halogen bulbs require a substantial volume of space tocontain the vacuum required to prevent air from destroying the filament,to keep the glass or silica envelope from overheating, and to insulatenearby objects from the emitted heat. In contrast, LEDs, as solid-statedevices, require much less space and generate much less heat. If thevolume of an incandescent or halogen bulb is allocated to a solid-stateLED light, considerably more functions may be incorporated into thelighting product.

Unlike incandescent and halogen lights, LEDs ordinarily produce light ina narrow, well-defined beam. While this is desirable for manyapplications, the broad-area illumination afforded by incandescent andhalogen lights is also often preferred. This is not easily accomplishedusing LEDs. The light produced by incandescent and halogen lights thatis not directed towards the target performs a useful function byproviding ancillary illumination and a decorative function. Halogenlights with their dichroic reflectors do this necessarily, but ordinaryincandescent lights can employ external shades, not part of the lightbulb, in a variety of artistic designs to make use of this otherwisemisdirected light.

SUMMARY

Embodiments of the present invention overcome the limitations of halogenor incandescent light sources, and combine their desirable propertieswith the advantages afforded by LEDs into a unique system. Variousembodiments include systems and methods that provide direct illuminationas well as decorative illumination distinct from the directillumination.

Embodiments of the present invention therefore include an LED-basedlight emitter (which includes one or more LEDs) for replacing standardincandescent and halogen bulbs for a wide variety of purposes. Inaccordance with various embodiments, lighting systems have enhancedfunctionality compared to that of conventional incandescent- orhalogen-based lighting systems, and typically include a decorativeillumination element that provides, e.g., decorative illuminationdistinct from the direct illumination from the light emitter.

Some embodiments include an electrical connector or base the same as orequivalent to a standard bulb base, a printed circuit board (or othercircuit substrate or module) electrically connected to the base, adriving circuit that may be mounted on or embodied by the printedcircuit board, and/or one or more LEDs of one or more colors that may beattached to the printed circuit board. The driving circuit may includeor consist essentially of a solid-state circuit that regulates thevoltage and current available from the electrical source (e.g., a powersocket) and regulates the output to a constant value utilized by theLEDs. The available source voltage may be either greater than or lessthan that utilized by the LEDs.

Various embodiments of the present invention include an LED lamp thatreplaces incandescent and/or halogen lamps as well as their decorativeshades by including LEDs on both sides of the printed circuit (PC)board, where the decorative LEDs may be on the opposite side of thatintended for direct illumination. The decorative LEDs may, for example,illuminate an envelope or shade around the lamp.

Lighting systems in accordance with various embodiments may also includeadditional circuitry, e.g., to allow remote control of lightingfunctions via an infrared or wireless device; to change the color ofeither or both of the (decorative) shade illumination and thedirect-illumination LEDs; to impart a time-varying color and/orintensity to the (decorative) shade illumination and/or the directillumination; to enable external switching via mechanical action ofcolor, pattern, and/or intensity on either the shade or directillumination; and/or to enable the switching of the various functions ofcolor, intensity, and/or pattern by interrupting the power to thecircuit within a predetermined time interval.

Mechanisms such as mechanical actuators that alter the pattern and colorof light to the shade for the purpose of decorative illumination mayalso be included. Such mechanisms may be or include a shadow screen, amulti-faceted mirror, or other reflective or diffractive opticalcomponent or components either fixed within the envelope of the lightingunit or which are configured to move in order to vary the pattern and/orcolor of the resulting light for decorative and/or direct-illuminationpurposes.

Various embodiments of the present invention feature one or moreadditional light emitters such as LEDs disposed within the envelope(housing) of the light bulb to provide the decorative illumination. Aseparate, secondary circuit may be used to produce a constant currentfor the additional, decorative light emitter(s) and control theirdecorative illumination characteristics such as intensity, color,pattern, and/or frequency. The secondary circuit may be connected to themain source of power. Light generated from the decorative lightemitter(s) may be guided along at least a portion of the length of anoptical component and exit the housing through openings on the shade ofthe housing. Such embodiments may include a secondary optical element todirect light generated by the light emitter for direct illumination(e.g., the primary-illumination LED(s)) to provide the decorativeillumination. A heat sink may be thermally connected to any or all ofthe light emitters for regulation of their temperature. A circuit mayprovide remote control of lighting functions of the lighting system(e.g., the decorative light emitter(s)) via, e.g., an infrared orwireless device.

One or more optical components may be disposed within the housing, andmay direct a first, larger (e.g., more intense) portion of lightgenerated by the light emitter(s) for direct illumination and direct asecond, smaller (e.g., less intense) portion of light for decorativeillumination. The second portion of light may be guided along the lengthof a secondary optical component and exit the housing through one ormore openings on the shade of the housing. In an alternative embodiment,the decorative illumination is achieved by light emission through aplurality of light paths connecting the housing and the opticalcomponent that directs the second portion of light from the lightemitter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention. In the followingdescription, various embodiments of the present invention are describedwith reference to the following drawing, in which:

FIG. 1 illustrates various views of an exemplary halogen illuminationdevice referred to commonly as an MR-16.

FIG. 2 illustrates various view of an embodiment of the presentinvention that can retrofit the halogen illumination device and containsLEDs for illumination on one side and LEDs for direct illumination onthe other. Circuitry to enable regulation and other features is alsoshown.

FIG. 3 illustrates various views of an embodiment of the presentinvention in which high intensity LEDs are placed on both sides toproduce shade illumination and direct illumination. A switch andcircuitry for changing the attributes of the lighting is also shown.

FIG. 4 illustrates various views of another embodiment of the presentinvention in which a movable, multifaceted mirror is included on theshade side of the illumination unit to provide a variable pattern on theshade.

FIG. 5A illustrates various views of another embodiment of the presentinvention in which an internal fixture containing apertures is includedto pattern illumination to the shade.

FIG. 5B is a sectional view of another embodiment of the presentinvention in which an additional LED is disposed within the housing toproduce decorative illumination.

FIG. 5C is a sectional view of another embodiment of the presentinvention in which decorative illumination arises from an opticalcomponent that directs light generated from the primary light emitter.

FIG. 5D is a sectional view of another embodiment of the presentinvention in which a plurality of the light paths, connecting thehousing and the optical component, direct a portion of the light fromthe primary light emitter for decorative illumination.

FIG. 6 shows elevational and top views of a means for producing aseries/parallel circuit comprised of individual LED semiconductor chipson a circuit board that results in a high-density lighting array.

FIG. 7 shows elevational and top views of an embodiment of thehigh-density LED array coupled with an integrated lens array that ismovable to produce variable-directional lighting.

FIGS. 8(a) and 8(b) schematically illustrate a constant-currentimplementation of a compact dc/dc boost converter with a feature thatenables current regulation of LEDs based on the thermal environment.

FIGS. 9(a) and 9(b) schematically illustrate a compact constant-currentbuck/boost circuit for current regulation based on the thermalenvironment in accordance with various embodiments of the invention.

DETAILED DESCRIPTION

FIG. 1 illustrates an incandescent halogen-type bulb commonly available.The features of this bulb derive from its operating characteristics: itoperates at high temperatures; it requires an evacuated envelopeseparated from the hot filament; it emits large quantities of infraredradiation experienced by the user as heat; and it consumes largequantities of electrical power. Nonetheless, these devices are in commonusage and fixtures and appliances have been constructed to accommodatethe form, fit, and function of these bulbs. This particular unit is amodel MR-16.

The essential components of the bulb include a connector 101 thatattaches to a standard source of electrical power (e.g., a power socket)that has a mating adapter; an evacuated transparent capsule 102containing the hot filament 105; an envelope 103 that acts as a shadeand filter to allow infrared radiation to pass, while reflecting aportion of the desirable visible light to the objects below; and atransparent front cover 104 that allows the radiation to pass, whileprotecting the evacuated capsule 102 from breakage.

FIG. 2 illustrates an embodiment of the current invention. Thisilluminating device preferably has the same form, fit and function asthe incandescent illumination device of FIG. 1 and as such has a similarelectrical connector 201 and similarly shaped transparent or translucentenvelope 202. The envelope 202 will generally act to scatter lightemitted from inside the envelope and be visible from the outside. Assuch, the envelope 202 may serve as a screen onto which are projectedand displayed images, colors or other decorative orinformation-containing light either visible to humans or at shorter orlonger wavelengths. The decorative or informational content may begenerated by circuitry contained on one or more circuit boards 206within the envelope of the bulb 202. This circuit 206 in its simplestform controls other illumination devices such as, e.g., the LEDs 207located on the back of the circuit board 204. Another circuit 205 may beused to control high-power LEDs 209 in an array 208 for directillumination of objects outside the envelope of the lighting device.However, this circuit or circuits may enable several useful features,including (i) a timer to adjust the color and illumination levelaccording to some preset or user-adjustable schedule, (ii) a photocellto turn the light on or off depending on the ambient light level and ora proximity sensor, (iii) a signaling function that communicates withother lights, and/or (iv) a user-accessible switch that enablesswitching of illumination characteristics such intensity, color, and/orcontinuous or flashing illumination modes.

Also typically located on circuit board 204 is a power-conditioningcircuit 205 that regulates power to the high-intensity LEDs 208 locatedon the underside of the board. This circuit adapts and controls thepower available via the connector 201 and conducted to the board viawires 203. The circuit 205 may contain storage features including abattery to enable the lighting device to act as an emergency lightsource in the event of a power failure. The circuit may rectify AC powerto DC to suit the desired current and voltage required by the seriesand/or parallel array of LEDs and provide power to other on-boardcircuitry.

In this embodiment, the LEDs 207 on the backside of the PC board 204 mayserve the function of communication and/or decoration. For decorativepurposes, the shade 202 is preferably made of a colored or whitetransparent (or preferably translucent) material such as plastic orglass that is textured to scatter light. In this manner light from theLEDs 207 impinges on this surface and is made more visible to the user,and may serve the function of decoration. The shade 202 may also containpenetrations 210 to allow heat to exit the LED enclosure.

FIG. 3 illustrates a similar incandescent replacement product. Thisproduct also contains an electrical connector 301, a shaped translucentor transparent envelope 302 with holes 310 to remove heat, one or moreprinted circuit boards 304 within the enclosure, and means such as wires303 to conduct electrical power to these board(s). This embodiment hashigh-intensity illumination LEDs 307 on the top surface and otherhigh-intensity LEDs 309 in an array 308 on the bottom surface. Unlikethe product of FIG. 2, which had small LEDs with a narrow exit beam andlow intensity, these high intensity LEDs 309 and 307 have a higher lightoutput (generally greater than 10 lumens), and the exit angle of thelight may range from a narrow angle to a very broad beam as desired. Tocontrol these LEDs, additional circuitry may be required as shown in thefigure. In addition to the power-transforming circuit 305 and thecontrol circuits 306, additional power handling circuits 311 may beincluded. The high-power LEDs may have one or more colored light outputsother than white, and have different orientations other than vertical toprovide decorative illumination above the lighting product. A switch 311that is accessible by the user may be used to control characteristics ofoperation of the lighting product.

FIG. 4 illustrates another embodiment of the present invention. Unlikethe previous examples in which modification of the color, intensity andpattern is performed by electrically controlling the electrical power toindividual devices of one or more orientations and/or color, thisembodiment contains a mechanical feature for varying the intensityand/or pattern with time. Variation is accomplished by, for example, amulti-faceted mirror 420, operated by a miniature electric motor 421that changes the orientation and position of the mirror. In this waylight is reflected or diffracted to form a pattern of shapes and/orcolor on the translucent or transparent envelope 402.

FIG. 5A illustrates another embodiment that includes a patterned mask520 (or other suitable means) that casts a shadow or other predeterminedpattern by blocking or otherwise modifying the pattern of lightemanating from the internal LEDs 507 located on the back side of thecircuit board 504. Other features from other embodiments discussedherein may also be incorporated.

FIG. 5B illustrates another embodiment in which an additional, separatelight emitter 531 (such as, e.g., one or more LEDs) is controlled and/orpowered by a main illumination circuit 532. The light emitter 531 may becoupled to separate and dedicated optics 533 to provide flexibility indesign, as light emitter 531 is generally meant to provide decorativeillumination that is distinct from and that complements the directillumination from the primary illumination source 534. For example, thedecorative illumination may be different from the direct illumination atleast in terms of illumination direction, color, and/or intensity. Poweris provided via connection of a power connector 535 to an input powersource, which, for example, may be either 115 VAC or 12 VAC. A circuit532 is preferably used to convert the alternating voltage to anapproximately constant DC current.

Light generated by the primary illumination source 534 may be directedby an optical component 536 (e.g., a total-internal-reflection (TIR)optic) and exit a substantially transparent cover 537 attached to thehousing (envelope) 538 to provide direct illumination. Electricalconnector (or circuit) 539 typically connects the light emitter 531 tothe circuit 532, which may produce a smaller constant current for thedecorative light emitter 531 than that for the primary illuminationsource 534. Electrical connector 539 may be connected to the main powersource; it may include or consist essentially of a resistor that limitscurrent to the decorative light emitter 531 and that is in parallel tothe primary illumination source 534. The circuit 539 may contain othersuitable electronics that modulate or adjust the decorativeillumination, such as the intensity, color, and/or frequency of thedecorative light emitter 531. The light from the decorative lightemitter 531 may be emitted in substantially the same direction as lightfrom the primary illumination source 534, but separate optics may beutilized to accomplish the desired decorative illumination. For example,light-guiding optics 533 may include an optical light guide or a solidplastic pipe that directs light along its length, creating a linear“stripe” of light down the outside of the device.

A heat sink 540 may be thermally connected to the thermal path of theillumination device and thus regulate the temperature of the primaryillumination source 534; the heat sink 540 may be co-linear with thelight-guiding optics 533. Characteristics of the decorative illuminationarising from light emitter 531, such as the intensity, color, frequency,and/or pattern of the light, may be responsive to a remote control thatmay be either optical (e.g., infrared), wireless (e.g.,radio-frequency), or wired (Ethernet, RS-232, etc.).

As described above, a backward-facing LED sharing a PCB with a primaryillumination source may be used for decorative illumination.Furthermore, a separate light emitter, e.g., with dedicated controland/or power circuitry, in the housing may provide decorativeillumination. In both cases, decorative illumination is formed activelyfrom a secondary light emitter providing its own light.

In another embodiment of the present invention, decorative illuminationis created passively via utilization of a portion of the light from theprimary illumination source. Reflecting optics may be used to directlight from light sources such as LEDs for direct illumination. Suchreflecting optics may be aluminized reflectors that may have a parabolicshape to enhance the directionality of the forward light. The optics mayalso include TIR optics, which utilize the refractive index differencebetween two different media to yield a reflective internal surface. TIRoptics are often very high efficiency (85-90%) compared to ordinarymetal-coated reflectors. The design of both types of reflectors isgenerally intended to maximize optical efficiency with the goal ofproviding the highest degree of illumination.

To provide illumination for decorative or other purposes not involvingdirect illumination, embodiments of the present invention use TIR andother reflecting optics to divert a portion of the light from itsotherwise intended path by modifying the optical design of the TIR andother reflecting optics. A portion of light may be “siphoned off” in acontrolled way and by means of reflection and refraction be redirectedto create the decorative or other non-direct-illumination function. Theredirected light may then be used to achieve the desired shape and colorfor decorative purposes.

FIG. 5C illustrates another embodiment of the present invention in whicha drive circuit 551 converts the mains voltage into a constant currentfor a primary illumination source 552 (e.g., one or more LEDs). An optic553 (which may include or consist essentially of, e.g., a TIR lens) maybe used to direct light generated by the primary illumination source552. A first portion of light generated by the primary illuminationsource 552 is guided for direct illumination, and a second portion oflight is guided for decorative illumination. The first portion of thelight is usually larger (i.e., more intense) than the second portion ofthe light. The first portion of the light generated by the primaryillumination source 552 may be directed by the optic 553 and exit asubstantially transparent cover 554 attached to the housing (envelope)555 to provide direct illumination. The housing 555 may include a shade(which may be substantially translucent) and one or more openings 556 inan optical component 557 (e.g., an optical waveguide that may becompletely or partially transparent) through which light may exit asdecorative illumination. Other approaches such as diffusion andfiltering of the light by the optical component 557 may be employed tofurther condition the light to meet specific decorative or secondaryillumination purposes.

FIG. 5D illustrates another embodiment of the invention operating viasimilar principles. One or more light channels 581 may connect a housing582 to an optical component 583 and be utilized to produce decorativeillumination therethrough. The light channels 581 may be, e.g.,substantially empty passages through the housing, or they may bepartially or substantially filled with an optical waveguide material. Aportion of the light generated by a primary illumination source 584(e.g., one or more LEDs) may be directed through the light channels 581and exit the housing 582 through complementary openings 585 on the shadeof the housing 582.

It may be appreciated from these descriptions that the LEDs used inthese embodiments, though small, occupy considerable space that limitsthe overall light output of the product. This is due, at least in part,to the need to provide electrical connections to each of thesemiconductor light-emitting chips that are housed in large packagesthat provide both electrical connections and a facility for removingheat and enabling passage of useful light. The packages also oftencontain a lens or mirror for shaping and directing this light. Whilethese packages allow some freedom of use, they also limit the densityand eliminate the ability to integrate the functions of heatdissipation, light direction and electrical connection. Many of thesefunctions may be accommodated within a printed circuit board ofappropriate design for a group of devices at the same time and withinthe circuit as it is formed.

One way of improving the light density of the overall product is toincorporate the light-emitting dies onto a suitable patterned circuitboard that contains the external circuitry needed to power and connectthe LED devices without the use of a package. FIG. 6 illustrates such anarrangement. This embodiment includes or consists essentially of aprinted circuit board having at least a middle portion 601 that may bethe usual fiberglass core or one that contains metals, ceramics or othermaterials to enhance thermal conductivity, a top metal clad layer 603,and a bottom cladding layer 602. It should be well understood that thesetop and bottom layers can easily be patterned by such processes asetching. A light-emitting assembly may be attached to the patternedsurface of cladding 603 by cementing it with a thermally andelectrically conducting compound, by welding it, or using any othersuitable attachment technique. The cladding 603 then may act as athermal or electrical conducting pathway, or both. The light-emittingassembly may include a metal base 604 to which is bonded a semiconductorlight-emitting chip 605. This light-emitting chip 605 typically containsa p-n junction that emits light and conducting top and bottom surfacelayers for electrical and thermal contact. A conducting wire or tabconnects the top conducting member of the junction to the oppositeconducting pad on the next assembly, thus building up a circuit that isin series. Using a different connection scheme, but the same generalapproach, a parallel connection may be assembled. By doing this, arelatively dense build-up of light-emitting chips may be assembled usingthe thermal and electrical transfer characteristics of the printedcircuit board. Furthermore, heat sinking, cooling or other componentsmay be attached to the board, improving performance, for example on theback side 602 of the printed circuit board. Although not shown, itshould be understood that this connection method may be extended in thetwo dimensions of the plane of the board.

Such chips as illustrated in FIG. 6 will generally emit light in alldirections. Such a distribution of light may not be desired for manylighting applications. Therefore, a matching array of lenses that ispositioned over the light-emitting chips may be utilized. Thisseparation of the top lens array from the LEDs allows the lens array tobe positioned independently, so that the light directed by the lens maybe moved and/or focused by moving the lens array in three dimensions.The movement may be controlled via, for example, stepper motors orpiezoelectric-activated motion controllers whose support electronics arealso contained on the printed circuit board. The array of lenses may bemolded from a transparent clear or colored material with a variety ofspherical or hemi-spherical shapes.

FIG. 7 illustrates such an arrangement. A PC board 701 containingpatterned metal traces 703 has located on its surface light-emittingportions featuring semiconductor light-emitting devices 705 that aremounted on bases 704. These areas are bonded together with electricallyconducting wires or strips to form a series/parallel circuit. Positionedover the top of these light-emitting regions is a lens array 710 intowhich has been formed (by a method such molding) a matching series ofoptical elements. Three such elements of two different shapes labeled711 and 712 are shown. This lens array 710 is spaced apart from thesemiconductor array and mounted to facilitate external manipulation inone or more of three dimensions as shown by the opposing pairs ofarrows. Hence, by moving the lens array 710, the light emitted from thematching LED array may be directed and focused as required, in essencesteering the light beam. This may be controlled by onboard electronics,and via remote control or such other means as required such as proximitysensors, timers and the like.

These lighting products generally require a source of AC or DC current.Although LEDs utilize direct current, it is possible to use the LEDs torectify AC power provided the number of LEDs is chosen to match the ACvoltage. It is well understood how to transform AC power to DC. The useof DC power as supplied by batteries, however, may present some problemsbecause as the battery voltage declines under load, the current drawn bythe LEDs rapidly declines, owing to the extremely non-linearcurrent-voltage characteristics of the diodes. Since the light output ofa LED is typically directly proportional to current (at least in someregimes), this means the light output rapidly declines. On the otherhand, if battery voltage exceeds a predetermined level, heating of thesemiconductor junction of the LED is excessive and may destroy thedevice. Moreover, excess heat in the LED junction may cause a conditioncalled thermal runaway, in which the heat raises the current drawn at agiven voltage, leading to further heating, which in turn leads togreater current draw and quickly destroys the device. This may be aparticular problem with high-power LEDs and requires careful thermalmanagement.

In order to help avoid this problem it may be useful to fix the currentthrough the LEDs rather than the voltage. Using a battery as the sourceof current, however, presents a problem because of the differing voltageand current behavior of the battery power source and the LED load.Therefore, a circuit may be utilized to regulate and fix the currentindependent of the voltage supplied by the battery. In the case wherethe battery voltage is less than the load voltage required by the seriesand/or parallel LED circuit, a boost circuit as shown in FIGS. 8(a) and8(b) may be employed. In these circuits an integrated circuit device,IC1 801, is used to control the charging and discharging of an inductorL1 803. This integrated circuit may be any of several that are availablesuch as the Texas Instruments TPS61040. After a charging cycle, the ICswitches the circuit so that the inductor L1 803 is permitted todischarge through the load, which in this case is the light-emittingdiodes 805. The current is controlled via a feedback resistor R1 806.The value of the resistor is chosen to fix the maximum current that ispermitted to flow through the load, which in this case, is one or moreLEDs (LED1, LED2) indicated at 805. This manner of control occursbecause the voltage drop across R1 806 is compared to an internallygenerated reference voltage at pin FB of IC1 801. When the two voltagesare equal the current is considered fixed and will be held to thatpredetermined value. A diode D3 802 is used to ensure protection of theIC1 801 in case the battery source (not shown) is connected backwards.The diode 804 allows current flow through the LEDs 805 in only theforward, or light-emitting direction. In embodiments of this invention,such a circuit may be enclosed within the envelope of the bulb.

The circuit shown in FIG. 8(b) differs from that of FIG. 8(a) in thatthe former contains an easy and inexpensive means of protecting the LEDsfrom excessive current flow and the runaway that results from hightemperatures. In this circuit a resistor with a positive resistance rateof change with temperature, R2 807 is placed in series with a fixedresistor. Resistor R2 is physically located on the circuit board so asto be in the thermal pathway of heat emanating from the LEDs 805.Therefore, when the temperature of the LEDs 805 increases, theresistance of R2 807 also increases, and its resistance is added to thatof R1 806. Since the voltage drop across these combined resistancesappears on the feedback pin FB of IC1 801, the increased voltage isinterpreted as a request for decreased current. Hence, the naturaltendency of the LEDs 805 to draw more current, which would ordinarilylead to the failure of the part, is averted by introducing aself-limiting control function.

This circuit has the advantage of being very efficient and compact andhaving built into it a temperature regulation that allows the resultingsystem to automatically adapt to the thermal environment in which it isplaced. Because of these attributes, it may, for example be put into aminiature lamp base of the kind used for flashlights (e.g., a PR-typeflange base).

However, one possible limitation of the circuit is that it may onlyboost voltage from a lower value to a higher value required by the LEDload. Therefore, in situations where only one LED is required, but ahigher input voltage is all that is available, the excess voltage willgenerally appear across the LED even if one of the circuits in FIG. 8are used. This may cause an excessive current to be drawn, leading topremature failure of the LED and/or premature draining of the battery.To solve this problem, embodiments of the invention feature a circuitthat is preferably still compact enough to fit into a bulb or bulb base,and that is capable of either raising or lowering the output voltageabove or below the voltage of the incoming battery or other DC supply inorder to maintain the desired current through the LED load. The circuitwill either boost the voltage if the input voltage is lower thanrequired by the LED or reduce the voltage if it is higher than thatrequired to sustain the necessary constant current through the LED. Itis understood that references to an LED connote one or more LEDs in aseries, parallel or series/parallel circuit. Furthermore, because of thedeleterious effects of temperature, this circuit typically has theability to regulate the current through the LED depending on the ambienttemperature. The ambient temperature may be determined by theenvironment as well as heat dissipated by the circuit and the LED.

Such a circuit is depicted in FIG. 9. This circuit utilizes a so-calledCuk converter that is ordinarily used as an inverting-switching voltageregulator. Such a device inverts the polarity of the source voltage andregulates the output voltage depending on the values of a resistorbridge. In the illustrated embodiment, the inverter circuit has beenaltered so that it acts to boost the voltage output or buck the voltageinput in order to maintain a constant current through the loadrepresented by one or more LEDs 905. The circuit incorporates anintegrated circuit IC1 901 such as the National Semiconductor LM2611 CukConverter or equivalent. In this circuit, the internal transistor of IC1is closed during the first cycle charging the inductor L1 902 from thebattery source indicated as Vbat. At the same time the capacitor C2 904charges inductor L2 903, while the output current to the LEDs 905 issupplied by inductor L2 903. In the next cycle the IC1 901 changes stateto permit the inductor L1 902 to charge capacitor C2 904 and L2 903 todischarge through the LEDs 905. The control of the charging power andcurrent through the load is performed by the resistor network includingor consisting essentially of R2 906 a and R3 907 a. The overall value ofthese resistors together with the current passing through the LEDs 905from ground, sets a voltage that appears on the feedback pin (FB) of IC1901. Resistor 907 a has a positive temperature coefficient so that itsresistance increases with temperature.

The current may also be altered to accommodate thermal effects such asheat dissipation by the LEDs, heat produced by the IC1 or other circuitcomponents and/or the ambient environmental conditions. This is effectedby a temperature-dependent resistor R3. In FIG. 9(a), resistor R3 907 ahas a positive temperature coefficient in which the resistance increaseswith temperature. The additive effect of the series circuit with R2 906a means that as temperature rises, the overall resistance of thecombination does also, leading to an increase in voltage drop. This inturn causes IC1 to decrease the output current to the LEDs 905. In FIG.9(b) the resistor network includes resistors in parallel and series. Inthis instance, resistors R2 and R4 906 b, 908 are fixed and resistor R3907 b is temperature-dependent with a positive temperature coefficient.The use of a parallel arrangement allows a greater freedom of choice oftemperature dependence than a simple series arrangement.

The terms and expressions employed herein are used as terms andexpressions of description and not of limitation, and there is nointention, in the use of such terms and expressions, of excluding anyequivalents of the features shown and described or portions thereof. Inaddition, having described certain embodiments of the invention, it willbe apparent to those of ordinary skill in the art that other embodimentsincorporating the concepts disclosed herein may be used withoutdeparting from the spirit and scope of the invention. Accordingly, thedescribed embodiments are to be considered in all respects as onlyillustrative and not restrictive.

What is claimed is:
 1. An illumination device comprising: a housing; apower connector for connecting the illumination device to a power socketand receiving an input power; a light emitter disposed within thehousing; a circuit for regulating the input power and providing theregulated power to the light emitter; and an optical component fordirecting a first portion of light generated by the light emitter fordirect illumination in a first direction and a second portion of lightgenerated by the light emitter for decorative illumination in a seconddirection, the second direction being different from the firstdirection, a plurality of light channels extending between the housingand the optical component for directing the second portion of light,thereby providing the decorative illumination.
 2. The illuminationdevice of claim 1, wherein the first portion of light is more intensethan the second portion of light.
 3. The illumination device of claim 1,wherein the first portion of light exits through a cover attached to thehousing to provide direct illumination.
 4. The illumination device ofclaim 3, wherein the cover is substantially transparent.
 5. Theillumination device of claim 1, wherein the housing comprises asubstantially translucent shade, the second portion of light exiting theshade to provide decorative illumination.
 6. The illumination device ofclaim 5, wherein the shade contains openings through which the secondportion of light exits the housing for providing the decorativeillumination.
 7. The illumination device of claim 1, further comprisinga secondary optical component for further conditioning the secondportion of light for decorative illumination.
 8. The illumination deviceof claim 7, wherein the further conditioned second portion of light andthe direct illumination are distinct in terms of at least one of adirection, a color, or an intensity.
 9. The illumination device of claim1, wherein the light channels are partially or substantially filled withan optical waveguide material.
 10. The illumination device of claim 1,wherein the light channels are substantially empty.
 11. The illuminationdevice of claim 1, wherein portions of the housing connected to thelight channels define openings allowing the second portion of light toexit the housing.
 12. The illumination device of claim 1, wherein thelight channels each extend in a substantially straight line from theoptical component to the housing.
 13. The illumination device of claim1, wherein, in each light channel, (i) a first portion of the lightchannel directs light generally towards the housing, the light notexiting the housing from the first portion of the light channel, and(ii) a second portion of the light channel, different from the firstportion, directs light in a direction approximately parallel to an outercontour of the housing, light exiting the housing from the secondportion of the light channel.
 14. The illumination device of claim 1,wherein the optical component comprises a total-internal-reflectionoptic.
 15. The illumination device of claim 1, wherein the light emittercomprises one or more light-emitting diodes.
 16. A method of using anillumination device to provide direct illumination and decorativeillumination, the method comprising: generating light with a lightemitter disposed within a housing; directing a first portion of lightgenerated by the light emitter outside the housing in a first directionfor direct illumination; and via an optical component disposed withinthe housing, directing a second portion of light generated by the lightemitter outside the housing in a second direction for decorativeillumination, the second direction being different from the firstdirection, wherein the second portion of light is directed through aplurality of light channels extending between the housing and theoptical component.
 17. The method of claim 16, wherein the lightchannels each extend in a substantially straight line from the opticalcomponent to the housing.
 18. The method of claim 16, wherein, in eachlight channel, (i) a first portion of the light channel directs lightgenerally towards the housing, the light not exiting the housing fromthe first portion of the light channel, and (ii) a second portion of thelight channel, different from the first portion, directs light in adirection approximately parallel to an outer contour of the housing,light exiting the housing from the second portion of the light channel.19. An illumination device comprising: a housing comprising asubstantially translucent shade; a power connector for connecting theillumination device to a power socket and receiving an input power; alight emitter disposed within the housing; a circuit for regulating theinput power and providing the regulated power to the light emitter; andan optical component for directing a first portion of light generated bythe light emitter for direct illumination in a first direction and asecond portion of light generated by the light emitter for decorativeillumination in a second direction, the second direction being differentfrom the first direction, wherein the shade contains openings throughwhich at least some of the second portion of light exits the housing forproviding the decorative illumination.
 20. The illumination device ofclaim 19, wherein the first portion of light is more intense than thesecond portion of light.
 21. The illumination device of claim 19,wherein the first portion of light exits through a cover attached to thehousing to provide direct illumination.
 22. The illumination device ofclaim 21, wherein the cover is substantially transparent.
 23. Theillumination device of claim 19, further comprising a secondary opticalcomponent for further conditioning the second portion of light fordecorative illumination.
 24. The illumination device of claim 23,wherein the further conditioned second portion of light and the directillumination are distinct in terms of at least one of a direction, acolor, or an intensity.
 25. The illumination device of claim 19, furthercomprising a plurality of light channels extending between the housingand the optical component for directing the second portion of light tothe openings in the shade, thereby providing the decorativeillumination.
 26. The illumination device of claim 25, wherein the lightchannels are partially or substantially filled with an optical waveguidematerial.
 27. The illumination device of claim 25, wherein the lightchannels are substantially empty.
 28. The illumination device of claim27, wherein portions of the housing connected to the light channelsdefine openings allowing the second portion of light to exit thehousing.
 29. The illumination device of claim 25, wherein the lightchannels each extend in a substantially straight line from the opticalcomponent to the housing.
 30. The illumination device of claim 25,wherein, in each light channel, (i) a first portion of the light channeldirects light generally towards the housing, the light not exiting thehousing from the first portion of the light channel, and (ii) a secondportion of the light channel, different from the first portion, directslight in a direction approximately parallel to an outer contour of thehousing, light exiting the housing from the second portion of the lightchannel.
 31. The illumination device of claim 19, wherein the opticalcomponent comprises a total-internal-reflection optic.
 32. Theillumination device of claim 19, wherein the light emitter comprises oneor more light-emitting diodes.
 33. A method of using an illuminationdevice to provide direct illumination and decorative illumination, themethod comprising: generating light with a light emitter disposed withina housing, the housing comprising a substantially translucent shade;directing a first portion of light generated by the light emitteroutside the housing in a first direction for direct illumination; andvia openings in the shade, directing a second portion of light generatedby the light emitter outside the housing in a second direction fordecorative illumination, the second direction being different from thefirst direction.
 34. The method of claim 33, wherein the second portionof light is directed through a plurality of light channels to theopenings in the shade, the plurality of light channels extending betweenthe housing and the optical component.
 35. The method of claim 34,wherein the light channels each extend in a substantially straight linefrom the optical component to the housing.
 36. The method of claim 34,wherein, in each light channel, (i) a first portion of the light channeldirects light generally towards the housing, light not exiting thehousing from the first portion of the light channel, and (ii) a secondportion of the light channel, different from the first portion, directslight in a direction approximately parallel to an outer contour of thehousing, the light exiting the housing from the second portion of thelight channel.